Since more than eighty percent of non-Hodgkins lymphomas in humans are of a B cell nature, and as several other well identified disease states, i.e. multiple myeloma Waldenstroms' macroglobulinemia, and other malignancies with an associated serum M component, reflect monoclonal B cell expansion, it is important to define the enhancing and suppressive influences capable of regulating B cell proliferation and differentiation. Only upon understanding the interactions of B cells with other regulatory cell types in the normal milieu will the conditions which result in malignancies of the B cell lineage be dissected and corrected. Thus the long term objective of this proposal is to understand the cellular and molecular mechanisms by which antigenically distinct T lymphocytes synergize to positively regulate the proliferation and differentiation of murine B cells. The model to be studied is the development of functional insulin specific help as two antigenically distinct T cells which are required for beef insulin stimulation of H-2b B cells have been cloned, characterized and shown to synergize to help trigger proliferation and differentiation of B cells. The hypothesis to be tested is that the T helper and T amplifier cell populations are differentially activated and/or act at discrete and distinct points in the sequential process of polyclonal and/or antigen specific B cell activation, proliferation, commitment to immunoglobulin secretion, and entry into the secretory state. Specifically, the proposal aims to evaluate the mechanism of activation of T helper and T amplifier cells and whether monoclonal populations of T helper and/or amplifier T cells transmit activation, proliferation, or differentiative signals to B cells by investigating the temporal and numerical requirements of helper and amplifier T cells during the development of functional insulin specific help. These events will be measured directly as activation of B cells for entry into cycle(GO to G1 transition), by the induction of increased levels of mRNA for J chain, and for the secretory form of the mu immunoglobulin heavy chain, by the alteration of the ratio of mRNA for the secretory to membrane form of mu heavy chain, by the appearance of cytoplasmic immunoglobulin, and finally by proliferation and differentiation of B cells.